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At least 199 records · Page 11Linked to original sources
PubMed2002

Excessive degradation of type II collagen in articular cartilage in equine osteochondrosis.

Articular osteochondrosis (OCD) occurs in both man and animals. The etiology remains to be determined. Studies of OCD lesions in animals may provide clues as to its pathogenesis. The aim of our study was to determine whether there was evidence for increased degradation namely proteoglycan (PG) release and type II collagen cleavage in articular cartilage harvested from OCD lesions. We examined ex vivo explants at post-mortem from equine OCD lesions and macroscopically normal site and age matched cartilage. These were cultured over a 10 day period in serum-free medium. Type II collagen cleavage was measured in articular cartilage and media using an Elisa assay to detect the COL2-3/4C(short) epitope, which is generated on cleavage of the triple helix of type II collagen by collagenases. PG release was measured by a dye-binding assay. Cumulative release of PG and COL2-3/4C(short) and their contents in cartilage at the end of the culture period were determined. In OCD lesions there was a significant increase in type II collagen cleavage by collagenase but no evidence for increase of PG degradation. These findings point to a selective increase in type II collagen cleavage by collagenases, in OCD lesions of the kind observed in osteoarthritis. Further work is needed to determine whether changes represent primary or secondary events in the pathogenesis of OCD.

Animals↗
PubMed2005

Biphasic surface amorphous layer lubrication of articular cartilage.

The biphasic nature of articular cartilage has been acknowledged for some time and is known to play an important role in many of the biomechanical functions performed by this unique tissue. From the lubrication point of view however, a simple biphasic model is unable to account for the extremely low friction coefficients that have been recorded experimentally, particularly during start-up. In addition, research over the last decade has indicated the presence of a surface amorphous layer on top of articular cartilage. Here, we present results from a finite element model of articular cartilage that includes a thin, soft, biphasic surface amorphous layer (BSAL). The results of this study show that a thin BSAL, with lower elastic modulus, dramatically altered the load sharing between the solid and liquid phases of articular cartilage, particularly in the near-surface regions of the underlying bulk cartilage and within the surface amorphous layer itself where the fluid load support exceeded 85%. By transferring the load from the solid phase to the fluid phase, the biphasic surface layer improves lubrication and reduces friction, whilst also protecting the underlying cartilage surface by 'shielding' the solid phase from elevated stresses. The increase in lubrication effectiveness is shown to be greatest during short duration loading scenarios, such as shock loads.

Biomechanical Phenomena↗
PubMed1976

The effect of hydrocortisone acetate on adult human articular cartilage.

Living adult human articular cartilage has been maintained in tissue culture for eight days. Cartilage explants were cultured in one of three concentrations of hydrocortisone acetate or as control explants without this drug. The concentrations of hydrocortisone used were 0.01 microng/ml, 0.1 microng/ml and 1.0 mg/ml. The amount of proteoglycan shed into the medium was measured and no significant difference was found between the explants exposed to hydrocortisone and those that were not. These results suggest that hydrocortisone does not have a catabolic effect on the proteoglycan of articular cartilage. The widely held view that intra-articular corticosteroid injection causes cartilage damage, must remain in doubt.

Adolescent↗
PubMed1980

[Structure and function of the fibrous structure of articular cartilage].

Structure of the articular cartilage fibrous stroma in the mature rabbit femoral heads has been studied and described by means demasking of fibres, of electron microscopy and polarization microscopy. A new scheme on the articular cartilage fibrous stroma structure is suggested, which differs from that of Benninghoff. A single fibrous cartilage framework consists of, at least, three networks of fibres directed to different sides. The role of every stromal part is interpreted in the whole function of the tissue.

Animals↗
PubMed1975

The ultrastructure and biomechanical significance of the tidemark of articular cartilage.

Thirty specimens of human articular cartilage obtained at surgery were examined by scanning electron microscopy to determine the ultrastructure of the tidemark, the junction of the non-calcified and calcified portions of mature articular cartilage. Three distinct variations of the collagen framework of the tidemark were observed: (1) A band of randomly oriented compacted fibrils that appeared to be continuous with those of the non-calcified and calcified zones. (2) A band of flattened fibrils paralleling the undulating surface of the calcified cartilage. (3) A band of perpendicularly oriented fibrils having a distinct continuous transition between the non-calcified and calcified zones, the amount of calcified material applied about the fibrils rapidly increasing as the fibrils entered the calcified zone. The tidemark may serve to provide a tethering mechanism for the relatively flexible and perpendicularly oriented collagen fibrils of the deepest portion of the non-calcified articular cartilage and may prevent them from being sheared at their point of anchorage to the calcified zone. The undulating pattern of the tidemark affords a strong geometric pattern in providing resistance to the shearing action of articulation. Small gaps present in the tidemark may provide pathways for the passage of nutrients into the deep non-calcified zone of articular cartilage from the subchondral bone.

Biomechanical Phenomena↗
PubMed1984

Heterogeneity of proteoglycan particles in thin sections and replicas of human articular cartilage.

Proteoglycans were studied in articular cartilage of human femoral condyles. On the basis of the histochemical data obtained by means of light microscopy (AB + CEC MgCl2; pre-incubation with hyaluronidase or with chondroitinase ABC), the proteoglycan concentration as well as the keratan sulfate-chondroitin sulfate ratio seemed to increase proportionally to the articular cartilage depth. AB-proteoglycan particles of various shapes (filament-like or leaf-like) and sizes (10 nm or 16-18 nm), depending on the articular cartilage depth and on the histochemical conditions (as above), were visualized in thin sections. Similar heterogeneity of elongated non-collagen particles was shown in replicas of fresh freeze-fractured and deep-etched specimens. An interpretation of the distribution and nature of articular cartilage proteoglycans was made by comparing the obtained morphological findings.

Adolescent↗
PubMed1996

The cellular physiology of articular cartilage.

The cells of articular cartilage, or chondrocytes, live in an unusual and constantly changing physicochemical environment. They receive poorly understood signals during the loading of the tissue and produce, through a balance between macromolecular synthesis and degradation, a mechanically resilient extracellular matrix. Matrix turnover is influenced by changes to the intracellular composition (cell volume, pH and ionic content) of chondrocytes, and there are suggestions that this is altered in the disease process of osteoarthrosis. However, there is little information on the fundamental aspects of articular cartilage cellular physiology, which is essential if the factors controlling cartilage integrity in health and disease are to be understood. The present short review focuses on some of the membrane transporters of chondrocytes involved in volume regulation, electrophysiology and the regulation of intracellular pH.

Adult↗
PubMedDate not supplied

Evidence for a distinct water-rich layer surrounding collagen fibrils in articular cartilage extracellular matrix.

Bovine articular cartilage was vitrified by high-pressure freezing. On the one hand vitrified samples were cryosectioned and investigated by cryoelectron microscopy in an unstained frozen hydrated state. On the other hand, they were freeze substituted in pure acetone, ethanol, or methanol, respectively, and subsequently embedded in Epon. Ultrathin Epon sections were poststained with uranyl acetate and lead citrate. The resulting ultrastructural representation was different for every protocol. The evaluation of the combined results provides evidence for a distinct water-rich layer surrounding collagen fibrils in articular cartilage extracellular matrix, which has not been recognized before. The possible composition and function of this layer is discussed.

Animals↗
PubMed2001

Clinical imaging of articular cartilage in the knee.

Assessment of articular cartilage has become an essential part of magnetic resonance (MR) evaluation of the knee. This has occurred because of recent advances in treatment along with improved accuracy of MR image evaluation of articular cartilage. Detection of articular cartilage defects can provide an explanation for symptoms and allow identification of patients for cartilage therapy and is an important factor for predicting prognosis of patients with knee injury. This review describes the most easily implemented MR techniques for evaluation of articular cartilage and the normal and abnormal appearance of cartilage seen using these techniques. The influence of imaging findings on treatment is described.

Cartilage, Articular↗
PubMed2003

Biomechanical properties of knee articular cartilage.

Structure and properties of knee articular cartilage are adapted to stresses exposed on it during physiological activities. In this study, we describe site- and depth-dependence of the biomechanical properties of bovine knee articular cartilage. We also investigate the effects of tissue structure and composition on the biomechanical parameters as well as characterize experimentally and numerically the compression-tension nonlinearity of the cartilage matrix. In vitro mechano-optical measurements of articular cartilage in unconfined compression geometry are conducted to obtain material parameters, such as thickness, Young's and aggregate modulus or Poisson's ratio of the tissue. The experimental results revealed significant site- and depth-dependent variations in recorded parameters. After enzymatic modification of matrix collagen or proteoglycans our results show that collagen primarily controls the dynamic tissue response while proteoglycans affect more the static properties. Experimental measurements in compression and tension suggest a nonlinear compression-tension behavior of articular cartilage in the direction perpendicular to articular surface. Fibril reinforced poroelastic finite element model was used to capture the experimentally found compression-tension nonlinearity of articular cartilage.

Animals↗
PubMed2002

Repairing large porcine full-thickness defects of articular cartilage using autologous chondrocyte-engineered cartilage.

Large full-thickness defects of articular cartilage remain a major challenge to orthopedic surgeons because of unsatisfactory results of current therapy. Many methods, such as chondrectomy, drilling, cartilage scraping, arthroplasty, transplantation of chondrocytes, periosteum, perichondrium, as well as cartilage and bone, have been tried to repair articular cartilage defects. However, the results are far from satisfactory. In this study, we applied a tissue-engineering approach to the repair of articular cartilage defects of knee joints in a porcine model. Using isolated autologous chondrocytes, polyglycolic acid (PGA), and Pluronic, we have successfully in vivo-engineered hyaline cartilage and repaired articular cartilage defects. The surface of the repaired defects appeared smooth at 24 weeks postrepair. Histological examination demonstrated a typical hyaline cartilage structure with ideal interface healing between the engineered cartilage and the adjacent normal cartilage and underlying cancellous bone. In addition, glycosaminoglycan (GAG) levels in the engineered cartilage reached 80% of that found in native cartilage at 24 weeks postrepair. Biomechanical analysis at 24 weeks demonstrated that the biomechanical properties of the tissue-engineered cartilage were improved compared with those at an earlier stage. Thus, the results of this study may provide insight into the clinical repair of articular cartilage defects.

Animals↗
PubMed2002

[Articular cartilage regeneration].

The main functions of articular cartilages are load-bearing and reducing friction of the articular surfaces. Because the capacity of articular cartilage to repair is limited, many attempts have been made to repair articular cartilage defects, which include transplantations of various tissues or cells. Within them, autologous cultured chondrocyte or autologous bone marrow mesenchymal cell transplantations are reported to be useful methods to repair articular cartilage defects. Here, we introduce these methods of tissue engineering and gene therapy, which are expected to become new treatments of articular cartilage defects.

English Abstract↗
PubMed1995

Cartilage oligomeric matrix protein: isolation and characterization from human articular cartilage.

Cartilage oligomeric matrix protein was purified in a native form from normal adult human articular cartilage. The key steps in the purification scheme were selective extraction with buffer containing EDTA, wheat germ agglutinin affinity chromatography, and removal of the related protein thrombospondin by heparin affinity chromatography. Particles of cartilage oligomeric matrix protein viewed by electron microscopy after rotary shadowing revealed structures similar to the prototype molecule purified from Swarm rat chondrosarcoma. The protein demonstrated a bouquet-like five-armed structure, with peripheral globular domains connected by thin flexible strands to a central assembly domain. Immunohistochemistry revealed age-dependent differences in the protein's distribution in cartilage. In normal human adult articular cartilage, there was a relatively uniform distribution throughout the interterritorial extracellular matrix, whereas in fetal articular cartilage, immunostaining was localized to the extracellular matrix directly adjacent to the chondrocytes. The isolation and characterization of human cartilage oligomeric matrix protein will facilitate its study in pathological conditions of human cartilage.

Adult↗
PubMed2003

Magnetic resonance imaging of focal articular cartilage lesions.

Lesions of the articular cartilage now are recognized as a common, often treatable source of joint disability. Magnetic resonance imaging (MRI) of articular cartilage is a sensitive, noninvasive method for the detection of focal articular cartilage lesions. Advancement in imaging technology now allows for high spatial resolution acquisitions that are able to identify most cartilage lesions, and these acquisitions can be incorporated into everyday clinical imaging protocols. Thus, screening for cartilage abnormalities can be accomplished, along with routine evaluation for ligament and meniscal abnormalities. Familiarity with the appearances of normal cartilage and the full spectrum of cartilage lesions will aid in specific diagnoses. Grading and sizing of cartilage lesions and any underlying bony abnormalities on MRI can help the surgeon in treatment planning; however, some significant cartilage lesions can be difficult to identify and grade by MRI.

Adolescent↗
PubMed1998

Inhibition of interleukin-1alpha-induced cartilage oligomeric matrix protein degradation in bovine articular cartilage by matrix metalloproteinase inhibitors: potential role for matrix metalloproteinases in the generation of cartilage oligomeric matrix protein fragments in arthritic synovial fluid.

OBJECTIVE: To determine whether matrix metalloproteinases (MMPs) degrade cartilage oligomeric matrix protein (COMP) to produce fragments similar to those found in synovial fluid (SF) from patients with arthritis. METHODS: COMP fragments were generated in vitro by treating (a) bovine articular cartilage with interleukin-1alpha (IL-1alpha), (b) purified bovine COMP with MMPs, and (c) articular cartilage with MMPs. The fragments generated in each case were analyzed by Western blot, using an antibody to the C-terminal heptadecapeptide of COMP. RESULTS: IL-1alpha stimulation of cartilage resulted in a fragmentation of COMP, which was inhibited by MMP inhibitors CGS 27023A and BB-94. Isolated, recombinant MMPs rapidly degraded purified COMP, as well as COMP residing in cartilage. Several COMP fragments produced in vitro had similar electrophoretic mobility to those in SF of patients with arthritis. CONCLUSION: MMPs may contribute to the COMP fragments found in vivo. Quantitation of MMP-specific fragments may be useful in the evaluation of MMP inhibitors in patients with arthritis.

Animals↗
PubMed1987

Effects of polysulfated glycosaminoglycan on chemical and physical defects in equine articular cartilage.

The effect of intra-articular polysulfated glycosaminoglycan (PSG) on repair of chemical and physical articular cartilage injuries was evaluated in 8 horses. In each horse, a partial- and a full-thickness articular cartilage defect was made on the distal articular surface of the radial carpal bone. In the contralateral middle carpal joint, a chemical articular cartilage injury was induced by injecting 50 mg of Na monoiodoacetate (MIA). Four of the 8 horses were not treated (controls), and 4 horses were treated by intra-articular injection of 250 mg of PSG into both middle carpal joints once a week for 5 treatments starting 1 week after cartilage injury. Horses were maintained for 8 weeks. There was less joint circumference enlargement in PSG-treated horses in MIA-injected and physical defect carpi, compared with that in controls. In MIA-injected joints, there was less articular cartilage fibrillation and erosion, less chondrocyte death, and greater safranin-O staining for glycosaminoglycans in PSG-treated horses. Evaluation of joints in which physical defects were made revealed no differences between control and PSG-injected joints. None of the partial-thickness defects had healed. Full-thickness defects were repaired with fibrous tissue (which was more vascular and cellular in PSG-injected joints) and occasionally small amounts of fibrocartilage. Seemingly, PSG had chondroprotective properties in a model of chemically induced articular cartilage damage, whereas PSG had no obvious effect in a physical articular cartilage-defect model.

Animals↗
PubMed1986

Investigations of low-temperature storage of articular cartilage for transplantation.

Isolated bovine articular cartilage chondrocytes and intact slices of cartilage were investigated to determine the effects of low-temperature cryopreservation on articular cartilage. Studies have focused on prefreezing conditions of cartilage, including the incubation medium and temperature of incubation, type and toxicity of the cryopreservative used, and the penetration of cryopreservative agents into cartilage cells. Cartilage freezing conditions were examined with respect to rate of freezing, controlled differential freezing rates, the ultimate storage temperature, and the time of storage. Cartilage thawing conditions were observed to ascertain the role of membrane osmotic stress during thawing and the effect of variable thawing rates on the viability of chondrocytes. Careful control of these variables can yield cartilage with cellular viability of over 50%. Optimum cryopreservation of viable cartilage should include prefreezing treatment with 7.5%-10% DMSO in nutrient medium, controlled slow freezing to -70 degrees, and rapid thawing in DMSO containing medium. A significant number of chondrocytes in deep-frozen cryopreserved articular cartilage can survive. The work recommends continued clinical use of deep-frozen cartilage.

Animals↗